It is known from German Pat. No. 1,182,414 to make bags from a multilayer thermoplastic strip workpiece, normally of polyethylene, in an apparatus having transport means for conveying the workpiece longitudinally in a transport direction along a path underneath an upper welding element having relative to the direction an upper upstream welding tool extending across the path and generally parallel thereto an upper downstream welding tool. Respective lower upstream and downstream welding tools are vertically aligned with the upper upstream and downstream tools and a blade extends transverse to the path between one of the upstream tools and the respective downstream tool. The upper and lower tools with the workpiece between them are relatively displaced toward one another to weld the workpiece together along upstream and downstream seams at the respective tools and to cut the workpiece across with the blade between the seams, and away from one another to free the severed downstream end section of the workpiece. Stacking means including a stack support downstream of the tools catches and holds the severed end sections in a stack.
A principal difficulty with this system is that the bags stick together at the seams in the stack. This is due to the fact that the seam regions are still quite warm when they are stacked up, and the seam regions are stacked right on top of each other in exact vertical registration so the still-hot seams can coalesce somewhat together. Sometimes the adherence is so great that the bags tear when an attempt is made to separate them.